821312540 has 24 divisors (see below), whose sum is σ = 1753033632. Its totient is φ = 323138880.

The previous prime is 821312537. The next prime is 821312549. The reversal of 821312540 is 45213128.

It is a super-2 number, since 2×821312540² = 1349108576722503200, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (821312549) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 335384 + ... + 337823.

It is an arithmetic number, because the mean of its divisors is an integer number (73043068).

Almost surely, 2^821312540 is an apocalyptic number.

It is an amenable number.

821312540 is an abundant number, since it is smaller than the sum of its proper divisors (931721092).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

821312540 is a wasteful number, since it uses less digits than its factorization.

821312540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 673277 (or 673275 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 26.

The square root of 821312540 is about 28658.5509054453. The cubic root of 821312540 is about 936.4892963089.

Adding to 821312540 its reverse (45213128), we get a palindrome (866525668).

The spelling of 821312540 in words is "eight hundred twenty-one million, three hundred twelve thousand, five hundred forty".